Many conventional photovoltaic (solar) panel arrays include a plurality of solar panels, optimally arranged for converting light incident upon the panels to electricity. Various support systems are used for attachment to roofs, free-field ground racks, tracking units, or other substrates/structures. Typically, these support systems are costly, heavy, structurally inferior, mechanically complicated and the installation is labor-intensive. Once the support structure is in place, mounting the solar panels on the support structure can be very difficult. It is further complicated by the tendency of some large solar panels to sag and flex, thereby rendering the panel mounting unstable. Panel repair and adjustment thereby become more difficult.
A conventional two-dimensional panel support system generally includes off-the-shelf metal framing channels having a C-shaped cross-section, such as those sold under the trademarks UNISTRUT™ or BLIME™. These are improvised for use as vertical and horizontal (or upper and lower) support members. The photovoltaic (solar) panels 12, or other panel-like structures, are directly secured to upper support members (30 in FIG. 3) and held in place by panel clips or panel holders 45 (as depicted in FIG. 3). These panel clips are manufactured in a wide range of sizes and shapes. The clips 45 are conventionally positioned and attached about the panel edges once each panel is arranged in place.
In a conventional, free-field ground rack system for mounting solar panels, (as depicted in FIG. 1) vertical support elements, such as I-beams 14, are spaced and securely embedded vertically into the ground. Tilt-mounting brackets 16 are secured to the top of each I-beam, such that a tilt bracket flange extends above the I-beam at an angle, as best seen in FIG. 2A. In this arrangement, two UNISTRUT™ lower joists 20 or a combined support structure 13 span the tilt-mounting brackets 16 and are secured thereto, using bolts 240 through apertures 216 (FIG. 3). As seen in FIG. 2B, UNISTRUT™ rails 30 are positioned across and fastened to lower joists 20. To secure each rail 30 to the corresponding lower joists 20, a bolt through a bolt-hole made in the rail sidewall attaches to a threaded opening in a nut plate (not shown) inserted inside the channel of the UNISTRUT™ joist. The nut-like plate engages and tightly secures against the upper flange of the joist's C-channels as depicted in FIG. 2A.
Once the bi-directional matrix span 10 is assembled, each solar panel 12 is secured in place by panel holding clips 45 connected using apertures 145 in panel rails 30 (FIG. 4). A select quantity of said clips is secured to the upper support rails about the perimeter of each panel. Each panel clip 45 is put in place and securely tightened to support rails 30. This installation process, especially if involving multiple clips 45, is often costly, inaccurate, dangerous and time-consuming.
Another example of a support system for panel-like structures is shown in U.S. Pat. No. 5,762,720, issued to Hanoka et al., which describes various mounting brackets used with a UNISTRUT™ channel. Notably, the Hanoka et al. patent uses a solar cell module having an integral mounting structure, i.e. a mounting bracket bonded directly to a surface of the back-skin layer of a laminated solar cell module, which is then secured to the channel bracket by bolts or slideable, engaging C-shaped members. Other examples of panel support systems are shown in U.S. Pat. No. 6,617,507, issued to Mapes et al.; U.S. Pat. No. 6,370,828, issued to Genschorek; U.S. Pat. No. 4,966,631, issued to Matlin et al.; and U.S. Pat. No. 7,012,188, issued to Erling. All of these patents are incorporated herein as reference.
Foldable support arrays 10 of upper support rails 30 and lower support joists 20 are found in the newer art developed by some of the inventors of the present application. One such example is depicted in FIG. 4. A detailed view of the intersection between upper support rail 30 and lower support joist 20 is depicted in FIG. 5. Some of the present inventors have developed a number of foldable support systems for solar panels and other panel-like structures. These are listed in the attached information disclosure documents.
The folding support arrays 10 of these support systems solve many problems well known in the art of panel array supports. However, even with a reliable, easily-deployed support array, there are still difficulties in the installation of the panels themselves, especially solar panel arrays. In particular, existing support systems require meticulous on-site assembly of multiple parts, performed by expensive, dedicated field labor. Assembly is often performed in unfavorable working conditions, i.e. in harsh weather or in difficult terrain, without the benefits of quality control safeguards and precision tooling. Misalignment of the overall support assembly often occurs, especially when mounting panels to the upper panel rails 30 with clips 45. This can jeopardize the supported solar panels.
Another problem is the spacing of the photovoltaic (solar) panels 12. It is important to accommodate panel expansion and contraction as a result of changes in the weather. Panels must, therefore, be properly spaced for maximum use of the bi-directional area of the span. Various geographical areas may require different panel spacing due to the distinct temperature patterns of each given location. It is also challenging to precisely space the panels on-site using existing support structures and panel clips 45, without advanced (and expensive) technical assistance.
For example, with one of the existing conventional designs described above (as depicted in FIGS. 2A and 2B), until the upper rails 30 are tightly secured to the lower support structure 13 of multiple support joists 20, each upper rail 30 is free to slide along the lower support joists 20 and, therefore, needs to be properly spaced and secured once mounted on-site. Additionally, since the distance between the two lower joists 20 is fixed on account of the drilled bolt-holes through the bracket, it is conventionally preferred to drill the holes on-site, so that the lower joists can be precisely aligned and attached through the pre-drilled attachment holes of the tilt bracket. Unfortunately, the operation of drilling the holes on-site requires skilled workers, and even with skilled installation, misalignment of the support structure and/or the solar panels supported by the structure may still occur (i.e. improperly spaced or slightly skewed from parallel).
The difficulties are compounded by the necessity of drilling holes 145 to accommodate connectors for the panel clips or holders 45. If this process is executed on-site, accurate placement of the solar panels becomes extremely difficult. Even if the apertures 145 are precisely drilled at the factory, an additional degree of imprecision is introduced when the panel clips 45 have to be connected to the upper support rails 30 while being positioned to hold panels 12. This is an awkward arrangement, even in the hands of expert installers. Normally, it is accomplished by connecting one (lower) portion of the panel clip 45 to the upper support rail 30, and then positioning panel 12 to be secured by another (top) portion of panel clip 45. Of necessity, this adds an additional assembly step for each panel clip 45, while still offering opportunities to accidently introduce misalignment in the overall panel array 10.
FIG. 5 includes a cross-sectional view and shows an improved prior art arrangement for mounting a panel array. Panels 12 are held using gaskets 130 in panel clip 45. The panel clip is held to panel rail 30 using aperture 145, though which a connector (not shown) holds the panel clip 45 to the panel rail 30. The panel rail 30 is held to support joist 20 by means of threaded connector 43, which extends from the bottom of the panel rail 30 through separating washer 24, through support joist 20 and into tilt-mount bracket 16. The through connector 43 is held by nut 44. Despite the effectiveness of this particular arrangement, there are still difficulties to be addressed, as elaborated on below.
Misalignment difficulties are exacerbated by the flexing of the panels 12 and sagging permitted by the natural flexibility of the panels. The sagging of the panels 12 can cause the panels to work out of their clips or holders 45. Improper installation, which occurs frequently in conventional systems, can lead to dislocation of the panels due to sagging or atmospheric conditions. The use of a wide variety of different mounting positions and panel array arrangements also worsens the stability problems caused by panel sagging or deflection. Further, certain mounting positions will make the panels 12 more vulnerable to atmospheric disruptions, such as those created by wind and precipitation. All of these variables also complicate electrical connections to the panels.
One method of correcting misalignment is through the use of larger and more effective panel clips 45. However, there are drawbacks in this approach. In particular, there are only a limited number of points at which panel clips can be connected. Accordingly, even with enlarged panel clips 45, only extremely limited portions of the lengths of panels can be secured.
The problems caused by misalignment due to sagging are further exacerbated in some environments by the accumulation of ice on the panels. This adds weight. Icing can also be a problem, particularly when water works its way into crevasses found throughout the overall panel array 10, and then freezes and expands. Still further, icing can become particularly problematic with respect to panel clips 45 extending beyond the panels 12 or the support rails 30. Accordingly, the use of larger panel clips 45 and increased numbers of them have typically added to the problems of ice formation on the overall panel array 10.
Therefore, a need exists for a low-cost, uncomplicated, structurally strong panel support system, and assembly method, so as to optimally position and easily attach the plurality of photovoltaic panels, while meeting architectural and engineering requirements. Further, there is an urgent need for a panel support system that will maintain the security of the mechanical connections of the solar panels to support rails despite the flexing of the panels (and support structure) caused by any of gravity, vibration, or environmental factors. Likewise, there is an urgent need to simplify the assembly of panel support systems, especially the connections between the upper support rails and panel clips. Such simplification should not compromise the stability or strength of the connections between the panels and the support system.
Conventionally, solar panels are supported at two opposite edges of the panel along the entirety of the panel length. This type of edge support, while convenient, permits panel buckling and loosening, as previously described. This in turn necessitates adjustments in the panel holding structures, which are often not successful since they are conventionally limited to two edges of the panel. An arrangement in which panels could be supported at positions other than two edges could eliminate many problems resulting from panel buckling, sagging, and loosening.
At present, none of the conventional panel support systems offer the capabilities of eliminating the problems mentioned above. An improved support system would achieve a precise configuration in the field without extensive work at the installation site. The use of such an improved system would facilitate easy, secure placement of solar panels onto the support structure prior to the final tightening of the panel clips. The shipping configuration of the improved support system would be such so as to be easily handled in transit while still facilitating rapid deployment.
Rapid deployment must be facilitated on any type of substrate providing stable support for the panels, without damaging or otherwise compromising the panels or substrate. Rapid deployment would also include rapid and secure mechanical connection of the panels using simple panel clips in a manner that would keep the panels secure despite loosening tendencies from panel sagging and flexing, or any number of other factors. Final panel clip tightening would not be necessary until all panels were in place. The preferred system would also minimize ice accumulation on the panel array, especially at the panel clips.